The present invention pertains generally to a system for providing a pressurized gas such as from separate gas cylinders in a pressure range to a single outlet with automatic changeover upon a reduction in cylinder pressure.
In the food service industry, it is the general practice to use tanks or cylinders on a one-at-a-time basis. Reaching of minimum acceptable pressure for carbonating drinks may occur at inconvenient times requiring personnel to interrupt service to customers to make a tank or cylinder substitution assuming a stand-by tank is on hand. The distraction of personnel from their primary task is undesirable. Secondly, to avoid accomplishing tank switching, personnel may continue to use a tank or cylinder when it is below satisfactory pressure. Weekly servicing of pressurized tanks has been proposed as a solution to the problem, but such servicing incurs a service charge per visit whether actually necessary or not.
In the prior art are switching valves as disclosed in U.S. Pat. No. 2,775,980 and 3,606,907 which include diaphragms. U.S. Pat. No. 2,138,988 discloses a switching valve with oppositely spring biased components which seat against inlet ports receiving pressure from different tanks. U.S. Pat. No. 2,389,667 shows bellows at 31-32 responsive to different pressure sources with bellows movement positioning a spindle to span and close a pair of needle valve orifices. U.S. Pat. No. 2,641,273 shows a switching valve for use in a carbonating system for beverages with a central valve stem and end mounted valves shifted axially in response to different tank pressures. Venting is via a loose fit between the valve stem and valve body. Gauges indicate tank pressure and cylinder in use indicator is provided.